1. Field of the Invention
This invention relates to an injection moulding tool with at least one central feed conduit, including one or more plates which are arranged over one another, at least one hot runner feed conduit with a branching point or with several branching points, in which a direction change and/or a division of the hot runner feed conduit is effected, for the feed of the hot injection moulding mass to two or more cavities.
2. Discussion of Related Art
Injection moulding tools are tools, by way of which plastic parts are manufactured. They are applied in injection moulding machines, in which an injection moulding mass is heated and in the molten condition is led via so-called hot runner feed conduits to the cavities, in which the respective plastic parts are moulded. Cooling channels which cool the region around the cavities so that the liquid plastic solidifies run in the region of these cavities.
Injection moulding tools must be regularly overhauled, since a certain erosion occurs, which however is relatively low. Deposits which occur in the hot runner feed conduits are more of a problem. These deposits occur to a more or less frequent extent, depending on the type of plastic. Deposits however generally occur with all plastics, independently of whether it is thereby the case of thermoplastics or duroplasts. Generally, it can however be said that the higher the processing temperature, the more deposits occur. Of course all regions of the injection mould which come into contact with the hot injection moulding mass are considered. However, it is known that deposits in the injection mould cavity tend to be inherent of a poor bleeding of the injection mould and tend to indicate a design fault, whereas deposits in the hot runner feed conduits unavoidably occur with certain plastics, even if no overheating is present.
As a result, one can assume that one main problem of the deposits occurs in the hot runner feed conduits, in the case of a correct design and temperature control. The cleaning of these hot runner feed conduits however requires a considerable amount of effort. The course of the hot runner feed conduits in the injection moulds is not at all in simple straight lines, but within the injection mould runs from one direction change point to the next in a straight manner or also from one branching point to the next branching point or from one direction change point to a branching point in a straight line.
An injection moulding tool of the state of the art is shown in FIG. 3. In the present embodiment, it includes two plates, specifically an upper base plate A and of a lower base plate B. On the one hand, the central hot runner feed conduit C is located in the upper plate A, and different hot runner feed conduits E lead from a branching point D in the horizontal direction. These hot runner feed conduits E are realized by a continuous horizontal bore and these bores are then closed by plugs G up to the direction change point F. The hot injection moulding mass via an injection valve J finally gets into a cavity H via a further section of the hot runner feed conduit F.
If the hot runner feed conduits need to the cleaned, then the plugs G need to be drilled out, the conduits cleaned and new plugs inserted thereafter. This effort cannot be carried out at the injection moulding business itself, and the respective injection mould must be sent back to the mould construction company where this service work is then carried out. A production interruption of at least several days, but mostly of several weeks thus arises.
Although different documents, such as Great Britain Patent Reference GB 1 299 094 or German Patent Reference DE 10 2008 045701-A or also EPO Patent Reference EP 2 263 845 B show injection moulding tools with hot runner feed conduits, these documents however concern themselves with other problems, for example with a special feed of these hot runner feed conduits, in order with this to reduce the build-up of deposits.